Merge pull request #1 from Kun-0546/feat/mode5-evolution-timeline

fix: remove dead code, fix test counts, add proper EN example report

feat: add Mode 5 tests and preview screenshots

feat: add Mode 5 — Topic Evolution Timeline

refactor: flatten cn/en into root with language selection

fix: use GraphQL API for repos >40k stars to get recent stargazer data

Sync CN mode names: 方向搜索→重点方向搜索, 深度关联分析→深度拆解

Refresh CN preview screenshots with translated growth pattern labels

Update CN mode names to Chinese and refresh preview screenshots

Update README_CN.md

Restructure: move skill files into github-trend-observer/ subfolder

Translate English labels to Chinese in CN reports

Rename to AI PM / Builder Skills, position GitHub Radar as Skill 1

Polish intro copy for both EN and CN

Improve intro paragraph breaks and section transitions